Reuters and the family ofsaid the concussion she suffered two weeks ago has led to a blood clot in her brain.
According to Reuters, "US Secretary of State Hillary Clinton has a blood clot in a vein between her brain and her skull, her doctors said Monday, predicting however she should make a full recovery." The family said the concussion had not resulted in a stroke.
She had been ill from a stomach virus, and in her dehydrated state she fainted and struck her head at her Washington, DC, home.
The BBC reported doctors performed a brain scan on Sunday that revealed the formation of a "right transverse sinus venous thrombosis"—a clot in the vein behind Clinton's right ear in the space between the brain and the skull.
"It did not result in a stroke, or neurological damage," said Drs. Lisa Bardack and Gigi El-Bayoumi, who were treating Clinton at New York's Presbyterian hospital.
Clinton, 65, had already announced her intention to retire after traveling to 115 countries in four years, a record. President Obama nominated Sen. John Kerry to succeed her.
The Fox network and Republican Party officials had said Clinton was suffering a "diplomatic illness," to avoid having to testify about the four American deaths at the Benghazi consulate in Libya. Although not able to testify, she did accept a strongly worded report condemning security for the facility, and said she took the blame. Four State Department officials involved resigned.